Home teeth whitening systems have been available since the late 1980's, acquired either through a dental professional or over-the-counter. Prior to these systems, persons desiring whiter or brighter teeth were subjected to various heat or light activated systems provided by their dental practitioner in the dental chair. Typically, these practices involved the dental practitioner applying a hydrogen peroxide solution on the teeth, protecting the sensitive soft tissues with a ligated rubber dam, and applying heat to the applied solution to effectuate oxidation. Such oxidation removed discoloration from the tooth surfaces.
With the greater consumer demand for cosmetically enhancing products, aesthetic dentistry has correspondingly grown. The demand for these products also created interest in products which could be administered at a more convenient time and place, and/or with less equipment. Thus, numerous products have since been developed which provide a person with the means to treat and whiten his or her teeth in the privacy and convenience of the home.
Generally, to begin the whitening process, a user is provided with a dental tray, either by a dental practitioner or as part of a purchased dental whitening kit. The tray is intended to retain the whitening composition at the desired location(s) and maintain contact between the tooth surface and the whitening composition. When the treatment involves a dental practitioner, the dental tray is typically custom fitted to the user's personal denition. Some dental practitioners may choose to have selectively enlarged tooth-treating compartments or reservoirs fabricated within the dental tray which are adapted to receive a sufficient amount of tooth whitening composition. The purpose for having such reservoirs is to provide more whitening composition and to ensure, if desired, long-lasting exposure of the teeth to the whitening agent. The dental tray loaded with whitening composition is typically worn by the patient for some extended period of time (e.g. 30 minutes to 8 hours), depending on the degree of discoloration the user desires to remove. This treatment is repeated over a sufficient period of time to effect the tooth whitening and bleaching process.
Whitening compositions are generally formulated with thickening rheological modifiers such as carboxypolymethylene, cellulosic polymers, or fumed silicas in order for the compositions to be provided as a thickened composition. For example, Pellico, U.S. Pat. No. 5,361,000 is directed to dental whitening compositions thickened with glycerin and carboxypolymethylene. Pellico, U.S. Pat. No. 5,718,886 discloses a stabilized anhydrous dental whitening composition utilizing Xanthum gum as a thickening agent.
During the intraoral application of a tray and whitening composition, a system can increase from ambient temperature of about 22-25.degree. C., to about 37.degree. C. As a result of this temperature rise, the whitening composition may have a tendency to decrease in viscosity and become more flowable. In addition, the composition may also become diluted from saliva moving in and out of the tray, resulting in dilution of the composition. This thinning and viscosity decrease creates a tendency for the composition and thus the whitening agent, to flow out of the tray, resulting in a reduced amount of whitening composition available for treatment at the target location for the desired length of time.
To overcome the effect of temperature and salivation, a series of patents by Fischer, namely U.S. Pat. Nos. 5,098,303; 5,234,342; 5,376,006; 5,409,631; 5,770,105; 5,725,843; and 5,746,598 disclose teeth whitening compositions characterized with high viscosity and stickiness to minimize dilution from saliva and prolong the period of time the whitening agent is in contact with the teeth surfaces. These patents describe the use of high concentrations of carboxypolymethylene to provide the high viscosity characteristic of the whitening composition as it is stored in its container.